The present invention relates to liquid, polymer containing compositions for use as thickening agents in aqueous mediums and, more particularly, to liquid, polymer containing compositions which can be used to viscosify brines to provide thickened aqueous well drilling and treating fluids.
The use of polymers such as hydroxyethyl cellulose (HEC) in fluids, e.g. brines, used in well drilling and treating fluids to improve viscosity, solids removal and/or filtration control has met with much success in past years. It is known, however, that the direct application of the dry powder form of these powders results in the formation of "fish eyes," i.e. unhydrated lumps of polymer, which can result in operational problems such as blinding of shaker screens and formation plugging. These problems can be minimized by adding the polymer in the form of a solution, colloid or other uniform suspension dispersed in a non-solvent carrier medium such as an oil-base liquid, e.g. diesel oil, kerosene. In co-pending Application Ser. No. 115,405 filed Jan. 25, 1980, there is disclosed one such HEC formulation which has met with great success. However, the composition disclosed in the aforementioned copending application suffers from the disadvantage that if the formulation is stored under static conditions for an extended period of time, some undesirable settling and hard packing of the HEC results. Redispersion of the HEC is time-consuming, requires special equipment and therefore is generally not conducive to on-site drilling, workover or completion operations.
Another disadvantage of the composition disclosed in the aforementioned co-pending application is that the composition, because it contains clay, is not completely acid soluble. As is well known, in the case of fluids used in workover and completion applications, it is desirable, and in some cases essential, that the fluid be acid soluble so that it can be displaced from the formation if necessary without damaging the formation.